A flyback converter is a switch mode power supply circuit that can be used in applications such as AC-to-DC adapters and battery chargers. FIG. 1 shows a block diagram of a conventional flyback converter 100. The flyback converter 100 utilizes a controller 120 to control a transformer. The transformer includes a primary winding 104 coupled to a DC source VBB, a secondary winding 106 coupled to a load 112, and an auxiliary winding 108. The controller 120 controls a switch 118 coupled in series with the primary winding 104. When the switch 118 is turned on, a current flows through the primary winding 104 and energy is stored in a magnetic core 124 of the transformer. When the switch 118 is turned off, a diode 110 coupled to the secondary winding 106 is forward biased, and thus the energy stored in the magnetic core 124 is released through the secondary winding 106 to a capacitor 122 and the load 112. An error amplifier 114 compares the current flowing through a current sense resistor 111 with a reference current to generate a feedback signal FB. The feedback signal FB is transferred to the controller 120 through an optical coupler 116. The controller 120 controls the switch 118 based on the feedback signal FB to adjust the output power of the transformer. However, this conventional flyback converter 100 has relatively large size. In addition, electromagnetic interference (EMI) exists during the operation of the flyback converter 100 due to electromagnetic induction of the transformer.